https://parts-per-million.itch.io/osr-solo
This solo rules supplement uses a handful of simple tables to try and emulate the DM/GM. Everything is a d6 bases, just as you would roll a d6 to test for wandering monsters, a d6 to check for secret doors and so on. The humble d6 has been controlling the D&D universe since the beginning.
Source: itch.io